Neutrophil to lymphocyte ratio and risk of a first episode of stroke in patients with atrial fibrillation: a cohort study

Summary Background The neutrophil to lymphocyte ratio (NLR) is associated with increased risk of cardiovascular morbidity and mortality. We aimed to assess the association between NLR and first episode of stroke in patients with atrial fibrillation. Methods Using the computerized database of the largest HMO in Israel, we identified a cohort of adults, aged 20 years or older, with atrial fibrillation diagnosed before 1 January 2012. Eligible subjects had no prior stroke or TIA, were not on anticoagulants at baseline, and had at least one blood cell count performed in 2011. The cohort (32 912 subjects) was followed for the first event of stroke or TIA until 31 December 2012. Results Overall 981 subjects developed stroke during a follow-up of 30 961 person-years (stroke rate, 3.17 per 100 person-years). The incidence rate of stroke increased across NLR quartiles: 2.27, 2.72, 3.26 and 4.54 per 100 person-years, respectively. Cox proportional hazard regression analysis adjusting for the individual CHA2DS2-VASc score risk factors showed that, compared with the lowest NLR quartile, the HR for stroke was 1.11 (95% CI, 0.91–1.35), 1.25 (1.03–1.51) and 1.56 (1.29–1.88) for the second, third and highest quartile, respectively. On stratified analysis, NLR refined the risk of stroke across all CHA2DS2-VASc score strata. Adding NLR to the CHA2DS2-VASc score increased the AUC from 0.627 (95% CI, 0.612–0.643) to 0.635 (0.619–0.651) (P = 0.037). Conclusions The neutrophil to lymphocyte ratio is directly associated with the risk of stroke in patients with atrial fibrillation. Future studies are needed to replicate these findings.